Training to Muscle failure

Whether or not training a set to muscular failure is better (or even necessary) for muscle growth, is a age old debate in bodybuilding. Muscular failure means doing reps in a set, until you can no longer lift the weight with proper form through the full range of motion.

Why is this last rep so important to discuss?

It may only seem like just another rep that happens to be the last in a set, but bodybuilders and scientist have viewed the last rep to failure as distinctly different from the other reps. Bodybuilders see it as giving it “your all” and fatiguing the muscle completely. Some high intensity workout programs, believe that you must go to failure for maximum muscle and strength gains.

Training to failure research studies:

To see why scientist see this rep differently, let’s look at some research.

A study published (J Appl Physiol. 2006 May;100(5):1647-56. Epub 2006 Jan 12.) did a 11 week resistance training program of failure vs nonfailure groups. Immediately after the 11th week all groups did the same workout, to see the effects each previous training led. Both groups had similiar increases in one rep max. During the 2nd phase of the study, there was an increase in muscular endurance in the failure group and power in the nonfailure group. The failure group had lower IGF-1 levels (important anabolic hormone for muscle growth), while the nonfailure group had lower resting levels of cortisol and higher testosterone levels.

A study published in (J Strength Cond Res. 2005 May;19(2):382-8) compared failure to nonfailure in 26 basketball players. The failure group did 4 sets of 6 repetitions every 260 seconds, whereas the nonfailure 8 sets of 3 repetitions every 113. Results showed that the failure group had significant strength increases over the failure group. One problem I have with this study is, time under tension differences between the sets. The failure group is doing 6 reps in a set instead of 3 reps. Even though the weight is the same and the time is lessened to increase intensity, 3 reps per set is not going to be the same stimulus.

A few months ago JM Willardson, who has published some important studies in excercise science, wrote a research note recently in(J Strength Cond Res. 2007 May;21(2):628-31.)
He acknowledged that there isn’t enough conclusive evidence yet, whether sets should be done to failure or not. However, willardson recommended advanced lifters use training failure to break past plateaus, due to increased activation of motor units and the hormonal response. He also didn’t recommend it long term due to overtraining and risk of injury.

Weight Training & Muscle Fiber Type Changes

You may have heard bodybuilders claim that weight training causes your muscle fibers to actually change types. The idea is that by specific weight training, you can help cause muscle fiber changes, which in turn make it easier for future muscle growth.

The muscles are made up of three major fiber types, I and IIA and IIB(roman numerals standing for type 1 and type 2A and 2B). Type 2 are fast twitch and for power. Type 2 contribute to most muscle growth(hypertrophy). TypeIIB are the most responsive to muscle growth and are colored white unlike the rest, which are red. Type one are slow twitch and mainly for endurance. Type once can still grow in diameter, but it’s not as significant. Each fiber type responds to different types of weights and rep ranges. Type 1 responds best to high reps light weight, whereas type 2 responds best to heavy weight with low reps per set.

The belief is that through training, some of these fiber types, will “act more like”, either a Type 1 or 2 fiber. In addition, you will also stimulate certain muscle fiber types for hypertrophy better than others. In order to do this, you must gear the weight training routine by the weight and reps you use. If you lift heavy with low reps to failure, you should get a increase in proprotion of type 2 fibers.

Muscle Fiber Type Research Studies:

A study published J Gerontol A Biol Sci Med Sci. 2000 Jul;55(7):B336-46 was done on 18 untrained older men. 9 did resistance training, while the other 9 served as a control. They did the resistance training for 16 weeks, 3 sets of leg press, half squat, and leg extension at 6-8 reps to failure with 1-2 minutes rest between sets. The results showed that I, IIA, IIB, fiber types all increased sized significantly. One interesting effect was that the proportion of type IIB fibers decreased and IIA fibers increased. Type IIB are a little more responsive to hypertrophy, but all fiber types hypertrophied, leading to a overall muscle size increase.

Another study published in (Eur J Appl Physiol Occup Physiol. 1990;61(1-2):37-41) was done on 12 college age men, comparing endurance resistance to strength training resistance excercises. One group did 7.5 weeks of muscular strength resistance training(heavy weight low reps), then took 5.5 weeks break, then continued for 7.5 weeks doing the endurance training(high reps lighter weight). The other group first started endurance resistance, then went to strength. The results showed that for the first phase, both types of training increased the fiber size of I, IIA, and IIB. However, the group that did strength phase 2nd, showed a increase in size in the I and IIB fiber types, but the endurance group in the 2nd phase showed decreased size in all fiber types. This study suggests that both types of training increase all fiber type sizes, but switching to endurance training after strength training, will reverse the hypertrophy gains.

Finally the study (Eur J Appl Physiol. 2002 Nov;88(1-2):50-60. Epub 2002 Aug 15.) was done on 32 untrained men for 8 weeks. They were divided into 4 groups (low rep, intermediate rep, high rep, and control). The low rep group did 3-5 reps to failure for 4 sets with 3 minutes rest between sets. Intermediate group did 9-11 reps for 3 sets with 2 minutes of rest. The high rep group did 20-28 reps with one minute rest. The excercises chosen were leg press, squat, and knee extension 2-3 times a week(2 for first 4 weeks, then 3 times a week for final 4 weeks). All muscle fiber types hypertrophied except in the control and high rep group. All groups however, did have a decrease in proportion of IIB fibers and increase in IIAB fibers. IIAB fibers will have less of the ability to increase in size than IIB. However, the low and intermediate rep group had a better overall hypertrophic result. This study suggests that the muscle fiber type changes happened equally with all training groups, however the lower rep ranges stimulated the type 2 fibers better, leading to more overall muscle hypertrophy. It appears that not even the 3-5 rep group could change the fibers to pure IIB fibers, but they were more effective in targeting these faster twitch fibers, leading to the more overall growth.

These studies show interesting results because it appears the common types of rep ranges bodybuilders do, will not change your muscle fiber to a higher proportion of IIB fibers(the ones most responsive to hypertrophy). It appears you would have to use an extremely heavy weight, one that would cause failure below 4 reps, to have a switchover to more pure IIB fibers. Focusing on only one type (IIB) is not the goal of bodybuilders however, as you would then be neglecting the other fiber types. Using very heavy weights is also hard on the joints and increases risk of injury. Even though there was no switchover to more proportion of IIB fibers in these studies, these more faster twitch fibers(IIB, IIAB, IIA) seemed to respond better to the heavier weights and thefore there was more overall hypertrophy.

Studies have also shown that there is a wide variance in the proportion of Type 2 to type 1 fibers, not only between each muscle, but between individuals. This is one major reason why, some people struggle to gain muscle, while others gain it with almost no effort. This is also why some people are more fit, for strength lifting or sprinting, while others are more suited for running or other endurance activities.

Forced Reps vs. Regular reps

The high intensity workout routine advocates such as HIT, often use forced reps as a way to increase the intensity of a set. Forced reps are when you do a few reps in a set beyond muscular failure. When you can no longer do the positive (concentric) motion of the rep, you have hit muscular failure. In order to continue with the set, you have a workout partner help lift the weight on the positive portion, for an additional 2 or 3 more reps, called forced reps. Is there really any benefit to doing forced reps? Let’s see what some studies have found.

Forced rep studies:

A study was published in Int J Sports Med. 2003 Aug;24(6):410-8. done on 16 athletes comparing forced reps to traditional reps. The traditional reps were 4 sets of leg presses, 2 sets of squats and 2 sets of knee extensions (with 12 repetitions) with a 2-min recovery between the sets and 4 min between the exercises. For the forced sets they chose a weight higher so they had to have assistance to complete 12 reps(to failure). Both types of rep sets led to large spikes in in serum testosterone, free testosterone, cortisol and GH concentrations. However the forced reps had larger increases in GH and cortisol. The more obvious part of the study results, was that it had more of an impact on strength (neuromuscular function).

Another study (Can J Appl Physiol. 2004 Oct;29(5):527-43) was also done comparing forced repetitions to regular. One group was 8 strength trained individuals with years of experience, while the other group was active, but not in strength training. The traditional rep group did squats for 4 sets with a 2-min recovery between sets for 12 reps to failure. The forced rep group did a higher weight, so they could complete 8, and an additional 4 with assistance. Both groups had a spike in serum testosterone, free testosterone, cortisol and growth hormone concentrations, with the trained athletes having a larger response. All the hormonal responses were greater in the forced rep sets than in the normal sets. The study also found a greater neurmuscular adaption. Researchers concludedthat the forced rep for experienced athletes, can be a good alternative, and may even be better than traditional sets.

Although forced reps seem to induce more stress on the CNS and hormones, whether or not that actually leads to “real world” better strength and muscle gains, is unclear from current research. Regardless, forced rep training should be looked at as a temporary workout parameter, due to the potential for injury and overtraining. Long term overuse of it, would release a lot of cortisol and overstress the CNS, leading to overtraining. The cons would outweigh the benefits in the long run, as you would be causing more stress to the body than is necessary for optimal muscle stimulation. Forced reps can be a good way however, to help shock your muscles into new growth, if you are currently on a plateau. Eventually your muscles will adapt to forced rep training and you will plateau again, just like with any training routine.

Good post yamaharob